Efforts will be made to culture the poisonous dinoflagellate, Gonyaulax tamarensis on a 100-200 liter scale and to isolate and chemically characterize the poisonous principle. A dihydro derivative and an hydrolysis product of saxitoxin, the paralytic shellfish poison produced by G. catenella, have been prepared in our laboratories, and will be examined to determine their chemical structures. Attempts will be made to attach these or other derivatives of saxitoxin to a protein carrier for production of antibodies needed for development of a radioimmune assay for saxitoxin. Regeneration of saxitoxin from the hydrolysis product will be attempted and if successful will be utilized to prepare C14-labeled saxitoxin.